Computer Telephony Integration In a Nutshell

CTI, or Computer Telephony Integration, is the conjugation of software, computers, and telephones. There are basically three layers of capabilities in CTI, each building on top of the other. When all three layers are combined and managed by intelligent, integrated, application software, the telephony possibilities are limitless. To one extent or another, all the CTI vendors support the following functions:


Receive a Call Place a Call with Caller Input Place a Call Using a Stored Number Predictive Dialing* Screen a Call End a Call

A PC telephony board can be connected to a twisted pair that carries just one channel of analog voice, or to a single twisted pair that carries 24 digital channels of T1 service (or 30 channels, in the case of the European E1 standard); and multiple connection combinations thereof. A single CTI-PC system can support many hundreds of lines.

*This feature has the computer instruct the phone system to begin calling a list of numbers, typically off a database or list. The predictive dialer seeks to establish if the line is busy; or if the call is answered, determine if it is an answering machine, fax, modem, or live person. If it is a person, the system then transfers the call right through to the calling party; i.e., a telemarketing agent.


Detect Telephone Number of Called Party Conference a Call* Forward a Call* Transfer a Call Automatically* Transfer a Call via Caller Input* Supervise a Call* Supervise a Transfer* Put a Call on Hold Notify a Party of a Second Call* Call Queuing*

* These capabilities are the classic PBX (private branch exchange) switching functions. Many or all of these PBX functions can be emulated by standalone PCs with special switching boards and software. Switching boards also permit sharing of a single fax board between multiple voice lines. Moreover, there are add-in cards/software that emulate the signals of proprietary PBX phones, thus freeing users of their PBX vendor entirely.


Define a Menu of Choices Callers Will Hear* Play Information to Callers* Change the Speed and Volume Level of a Message Speak Information Stored in an Electronic File*

* These features are also the province of Interactive Voice Response (IVR), or database lookup using TouchTone input. When you call your bank for account status, and step through menu options, you are using IVR. Voice Mail systems also overlap many of these IVR-style functions.


Broadcast a Message Notify a Called Party About a Stored Message Send a Fax Store/Forward a Fax Broadcast a Fax


Record and Store Information from Callers Receive/Store a Fax Detect Telephone Number of Calling Party Collect Dialed Digits Call Logging


Recognize a Spoken Command (Speaker Dependent) Recognize a Spoken Command (Speaker Independent) Verify a Caller's Claimed Identity Voice Cut-Thru VoiceStop Word Spotting

Many of these speech recognition functions are commonly handled by DSPs (digital signal processing chips). DSPs offer much higher performance, as well as offer more flexibility, than general purpose computer CPUs. It is also possible to have one PC-based DSP board handle all voice/answering machine/fax functions (see DSP sidebar).


Tone Detection* Custom Tone Detection* Generate Standard Network Tones* Custom Tone Generation* Recognize When a Call is Disconnected Detect a Human Voice** Detect an Answering Machine**

* DTMF, or dial tone functions, are normally handled by your PBX, PC-CTI system, or your local telephone company switch. However, it is also possible to send DTMF-type functions over a LAN, as well. Novell, via TSAPI, and soon, NT Server via TAPI, support such LAN-based signaling.

** These functions would be used, for example, by a predictive dialer.


Take the basic functionality, and add host/server access, and you get the following capabilities:

Automate interaction between caller and computer database. Reduce need for personnel by automating transactions. Permits distributed architectures -- connect one computer telephony system to another via a LAN. Store information remotely (accessible via LAN). Increase capacity by storing information remotely.

It is possible, via numerous off the shelf software packages and development tools, to interactively link a variety of databases (many of these packages support ODBC - Open Database Connectivity) into a telephony application.


Take the Basic Functionality with Integrated Host/Server Access, add agents or operators, and you enhance the telephony systems with the following capabilities:

Provide live operator assistance with access to automated directory information. Assistance can be provided in front of, or behind the PBX switch, to best utilize switch resources.

Agents can answer calls and have automatic access to database information about callers.

Provide agents with automatic dialing of phone numbers stored in a database.

Supervise calls to monitor interaction between caller and systems

Provide live operator assistance for placing calls (as in operator services) or when caller needs assistance beyond that offered by an automated system.

In the above, the term 'operator' is broadly used. It can also encompass a user at a desktop with an integrated CORBA compliant application for doing stock brokerage, VBX-enabled vehicle dispatch, telephony integrated Lotus Notes systems for dispensing medical services, etc. The possibilities of CTI are limited only be the user's imagination.

Note: some source material in this section came from Dialogic Corporation


21st, The VXM Network,